U.S. patent application number 13/996428 was filed with the patent office on 2013-10-17 for vibrating gyroscope and corresponding manufacturing process.
This patent application is currently assigned to Sagem Defense Securite. The applicant listed for this patent is Alain Jeanroy. Invention is credited to Alain Jeanroy.
Application Number | 20130269433 13/996428 |
Document ID | / |
Family ID | 44342207 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130269433 |
Kind Code |
A1 |
Jeanroy; Alain |
October 17, 2013 |
VIBRATING GYROSCOPE AND CORRESPONDING MANUFACTURING PROCESS
Abstract
The invention relates to a vibrating gyroscope (1),
characterised in that it comprises a base (2), a resonator (3)
comprising a body (4) of generally cylindrical shape terminating in
a distal face (5), to the side opposite the base (2), said face (5)
comprising at least one through hole (13), a plurality of
piezoelectric elements (10) placed in contact with the resonator
(3), vibration control and processing modules (18) arranged at
least in part on the base (2), and at least one electrical
connection (15) passing through the body (4) of the resonator (3)
via said hole (13), and electrically connecting said modules (18)
of the base (2) and the plurality of piezoelectric elements (10)
for controlling and measuring the vibration of the resonator
(3).
Inventors: |
Jeanroy; Alain; (Paris,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jeanroy; Alain |
Paris |
|
FR |
|
|
Assignee: |
Sagem Defense Securite
Paris
FR
|
Family ID: |
44342207 |
Appl. No.: |
13/996428 |
Filed: |
October 27, 2011 |
PCT Filed: |
October 27, 2011 |
PCT NO: |
PCT/EP11/68907 |
371 Date: |
June 20, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61488938 |
May 23, 2011 |
|
|
|
Current U.S.
Class: |
73/504.12 ;
29/25.35 |
Current CPC
Class: |
G01C 25/00 20130101;
G01C 19/5691 20130101; G01C 25/005 20130101; G01C 19/56 20130101;
Y10T 29/42 20150115 |
Class at
Publication: |
73/504.12 ;
29/25.35 |
International
Class: |
G01C 19/56 20060101
G01C019/56; G01C 25/00 20060101 G01C025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2010 |
FR |
1005070 |
Claims
1. A vibrating gyroscope (1), characterised in that it comprises: a
base (2), a resonator (3), comprising a body (4) of generally
cylindrical form terminating in a distal face (5), to the side
opposite the base (2), said face (5) comprising at least one
through hole (13), a plurality of piezoelectric elements (10),
arranged in contact with the resonator (3), modules (18) for the
control and processing of the vibration, arranged, at least in
part, in the base (2), and at least one electrical connection (15),
passing through the body (4) of the resonator (3) via said hole
(13), and electrically connecting said modules (18) of the base (2)
and the plurality of piezoelectric elements (10) for controlling
and measuring the vibration of the resonator (3).
2. The gyroscope (1) as claimed in claim 1, in which: said face (5)
comprises a plurality of through holes (13) arranged on its
circumference, and said gyroscope (1) further comprises a plurality
of electrical connections (15) passing through at least one
sub-assembly of said holes (13) for electrical connection of the
modules (18) of the base (2) with the plurality of piezoelectric
elements (10).
3. The gyroscope (1) as claimed in claim 2, in which: the holes
(13) are arranged substantially uniformly on the circumference of
the face (5), and the piezoelectric elements (10) are arranged
between said holes(13).
4. The gyroscope (1) as claimed in claim 1, comprising an
interconnection circuit (20) connecting the plurality of electrical
connections (15), and being connected to the piezoelectric elements
(10).
5. The gyroscope (1) as claimed in claim 1, comprising a linking
foot (21) between the resonator (3) and the base (2), said foot
(21) being arranged at the level of the extension of a central hole
(13) of the face (5) of the resonator.
6. The gyroscope (1) as claimed in claim 5, in which the control
and processing modules (18) of the base (2) and the piezoelectric
elements (10) are connected by at least one electric connection
passing through the linking foot (21).
7. The gyroscope (1) as claimed in claim 1, in which: part of the
piezoelectric elements (10) is capable of detecting vibrations of
the resonator, and the other part of the piezoelectric elements
(10) is capable of exciting the resonator in vibration.
8. The gyroscope (1) as claimed in claim 1, in which each
piezoelectric element (10) at the same time comprises a sub-element
(23) capable of detecting vibrations of the resonator and a
sub-element (24) capable of exciting the resonator in
vibration.
9. The gyroscope as claimed in claim 8, in which the resonator is
capable of vibrating as per a first vibration mode comprising
antinodes distributed over two axes, a second vibration mode
comprising antinodes distributed over two other axes, the face of
the resonator on each axis of the first and of the second vibration
mode comprising two piezoelectric elements (10), each piezoelectric
element (10) at the same time comprising at least one piezoelectric
sub-element (23) capable of exciting the resonator in vibration and
at least one piezoelectric sub-element (24) capable of detecting
vibrations of the resonator.
10. A production process of a vibrating gyroscope (1), comprising
steps consisting of: providing a base (2), forming a resonator (3),
comprising a body (4) of generally cylindrical form terminating in
a distal face (5), to the side opposite to the base (2), said face
(5) comprising at least one through hole (13), disposing a
plurality of piezoelectric elements (10) in contact with the
resonator (3), mechanically assembling the resonator (3) on the
base (2), placing vibration control and processing modules (18) in
the base (2), and electrically connecting said modules (18) of the
base (2) and the plurality of piezoelectric elements (10) via at
least one electrical connection (15) passing through the body (4)
of the resonator (3) via said hole (13), for controlling and
measuring the vibration of the resonator (3).
Description
GENERAL TECHNICAL FIELD
[0001] The invention relates to a vibrating gyroscope and a process
to make such a gyroscope.
STATE OF THE ART
[0002] Vibrating gyroscopes are currently used in numerous fields,
especially because of their solidity, their reduced electrical
consumption, and their rapid execution.
[0003] These gyroscopes comprise a resonator which can take various
forms, such as a bell or a tuning fork.
[0004] The invention relates more particularly to resonators
comprising a body of generally cylindrical shape.
[0005] The axis z is conventionally designated as the axis of the
cylinder, the axes x, y being arranged in the plane orthogonal to
the axis z.
[0006] It is known that such a resonator in vibration deforms
itself preferably elliptically, with four vibration antinodes
regularly arranged over the circumference of the cylinder in the
plane x, y. A first vibration mode 53, 57 of the resonator is
illustrated in FIG. 1, at two given instants, relative to its rest
state 54. The resonator passes from ellipse 53 to ellipse 57 at the
end of a semi-period, but this is still the same vibration
mode.
[0007] Any rotation of the gyroscope about the axis z generates
Coriolis forces which have a tendency to cause offset in rotation
of vibration antinodes about the circumference of the cylinder.
Piezoelectric detection elements, placed at the level of the
vibration antinodes, measure a signal which variation determines
the angular rotation speed and/or the angle of rotation about the
axis z.
[0008] By way of illustration, it is evident in FIG. 1 that
rotation of the resonator causes secondary vibration in elliptical
mode 52, 58 whereof the principal axes x.sub.1, y.sub.1 are located
at 45.degree. from the axes x, y. Vibration passes from ellipse 52
to ellipse 58 at the end of a semi-period.
[0009] The signal measured by the piezoelectric detection elements
at the level of these axes especially determines the angular
rotation speed.
[0010] In general, gyroscopes comprise four piezoelectric detection
elements for maintaining the vibration of said resonator, and four
other piezoelectric elements for measuring the vibration signal of
the resonator. These eight elements are most often arranged
uniformly about the resonator (four on axes x, y and four on axes
x.sub.1, y.sub.1).
[0011] However, the gyroscopes with cylindrical resonator known to
date have the disadvantage of being less compact and difficult to
manufacture. Also, they are highly sensitive to the vibratory
environment.
[0012] Therefore a solution improving devices of the prior art
should be proposed.
PRESENTATION OF THE INVENTION
[0013] For this purpose, the invention proposes a vibrating
gyroscope characterised in that it comprises a base, a resonator,
comprising a body of generally cylindrical shape terminating in a
distal face, to the side opposite the base, said face comprising at
least one through hole, a plurality of piezoelectric elements
placed in contact with the resonator, modules for vibration control
and processing, arranged at least in part in the base, and at least
one electrical connection passing through the body of the resonator
via said hole, and electrically connecting said modules of the base
and the plurality of piezoelectric elements for controlling and
measuring the vibration of the resonator.
[0014] The invention is advantageously completed by the following
characteristics, taken singly or in any of their technically
possible combinations: [0015] the face comprises a plurality of
through holes arranged over its circumference, and said gyroscope
also comprises a plurality of electrical connections passing
through at least one sub-assembly of said holes for electrical
connection of the base modules with the plurality of piezoelectric
elements; [0016] the holes are arranged substantially uniformly
over the circumference of the face, and the piezoelectric elements
are arranged between said holes; [0017] the gyroscope comprises an
interconnection circuit connecting the plurality of electrical
connection, and being connected to the piezoelectric elements;
[0018] the gyroscope comprises a linking foot between the resonator
and the base, said foot being arranged at the level of the
extension of a central hole of the face of the resonator; [0019]
the control and processing modules of the base and the
piezoelectric elements are connected by at least one electrical
connection passing through the linking foot; [0020] part of the
piezoelectric elements is capable of detecting vibrations of the
resonator and the other part of the piezoelectric elements is
capable of exciting the resonator in vibration; [0021] each
piezoelectric element at the same time comprises a sub-element
capable of detecting vibrations of the resonator and a sub-element
capable of exciting the resonator in vibration; [0022] the
resonator is capable of vibrating according to a first vibration
mode, comprising antinodes distributed on two axes, and a second
vibration mode comprising antinodes distributed on two other axes,
the face of the resonator on each axis of the first and of the
second vibration modes comprising two piezoelectric assemblies,
each piezoelectric assembly at the same time comprising at least
one piezoelectric sub-element capable of exciting the resonator in
vibration and at least one piezoelectric sub-element capable of
detecting vibrations of the resonator.
[0023] The invention likewise proposes a making process of a
vibrating gyroscope, comprising steps consisting of providing a
base, forming a resonator comprising a body of generally
cylindrical form terminating in a distal face, to the side opposite
the base, said face comprising at least one through hole, disposing
a plurality of piezoelectric elements in contact with the
resonator, mechanically assembling the resonator on the base,
placing vibration control and processing modules in the base, and
electrically connecting said base modules and the plurality of
piezoelectric elements via at least one electrical connection
passing through the body of the resonator via said hole for
controlling and measuring vibration of the resonator.
[0024] The invention has numerous advantages.
[0025] An advantage of the invention is to propose a more compact
vibrating gyroscope.
[0026] An advantage of the invention is to propose a vibrating
gyroscope having a lower angular derive.
[0027] Another advantage of the invention is to propose a gyroscope
easier to manufacture.
[0028] Yet another advantage of the invention is to propose a
gyroscope having lower production costs.
[0029] Finally, another advantage of the invention is to propose a
gyroscope less sensitive to the vibratory environment.
PRESENTATION OF FIGURES
[0030] Other characteristics, aims and advantages of the invention
will emerge from the following description which is purely
illustrative and non-limiting and which must be considered with
respect to the attached diagrams, in which:
[0031] FIG. 1, already commented on, is an illustration of
vibration modes of a gyroscope with cylindrical resonator;
[0032] FIG. 2, is an illustration of an embodiment of a gyroscope
according to the invention;
[0033] FIG. 3 is an illustration of an embodiment of a base of
gyroscope according to the invention;
[0034] FIG. 4 is an illustration of another embodiment of a
resonator of a gyroscope according to the invention;
[0035] FIG. 5 is an illustration of an embodiment of a resonator
comprising a piezoelectric element according to the invention;
[0036] FIG. 6 is an illustration of another embodiment of a
vibrating gyroscope according to the invention;
[0037] FIG. 7 is a schematic illustration of steps of a treatment
process according to the invention;
[0038] FIG. 8 is a schematic illustration of a embodiment of the
processing of the vibration according to the invention;
[0039] FIG. 9 is an illustration of an embodiment of the control
and processing of the vibration of the resonator.
DETAILED DESCRIPTION
[0040] FIG. 2 shows an embodiment of a vibrating gyroscope 1
according to the invention.
[0041] The gyroscope 1 comprises a base 2, which acts as plinth.
The gyroscope 1 also comprises a certain number of vibration
control and processing modules 18, described later, and placed at
least in part in the base 2. In general, these modules 18 are
arranged on an electronic control card integrated into the lower
part of the base 2, and covered by a protective cap.
[0042] The gyroscope 1 also comprises a resonator 3. This resonator
3 comprises a body 4 of generally cylindrical shape terminating in
a distal face 5, to the side opposite the base 2.
[0043] The resonator 3 is generally a metallic piece.
[0044] The face 5 is particular in that it comprises at least one
through hole 13. In the embodiment of FIG. 2 the face 5 comprises a
plurality of through holes 13.
[0045] The gyroscope 1 also comprises a plurality of piezoelectric
elements 10, placed in contact with the resonator 3.
Advantageously, these piezoelectric elements 10 are disposed on the
face 5 of the resonator 3, turned to the exterior of the resonator
3. These piezoelectric elements 10 are designed to measure the
vibration of the resonator 3 and maintain it. These are generally
piezoelectric electrodes.
[0046] For example, it is known to use lead zirconate titanate as
piezoelectric material.
[0047] The gyroscope 1 has at least one electrical connection 15,
passing through the interior of the body of the resonator 3 via
said hole 13, and electrically connecting said modules 18 of the
base 2 to the plurality of piezoelectric elements 10, for
controlling and measuring the vibration of the resonator 3. This
connection 15 could be relayed by an interconnection card 20,
acting as an interface between the connection 15 and the
piezoelectric elements 10.
[0048] As is it evident, this configuration creates a highly
compact gyroscope, since the electrical connections between the
control and measuring modules 18 and the piezoelectric elements 10
are made via the interior of the body of the resonator 3, via at
least one dedicated hole 13 of the face 5 of the resonator 3
opposite the base 2.
[0049] Advantageously, the face 5 comprises a plurality of through
holes 13 arranged on its circumference, as illustrated in FIGS. 2
and 4.
[0050] In this case, the gyroscope 1 also comprises a plurality of
electrical connections 15 passing through at least one sub-assembly
of said holes 13, for the electrical connection of the modules 18
of the base 2 and the plurality of piezoelectric elements 10.
[0051] The rest of the holes can be used for the entry of
mechanical links, for example rods 22 serving to mechanically link
the interconnection card 20 with the base 2.
[0052] Advantageously, the holes 13 are arranged substantially
uniformly over the circumference of the face 5, that is, with
regular or quasi-regular angular offset.
[0053] In this case, it is advantageous to place the piezoelectric
elements 10 between said holes.
[0054] Advantageously, the holes 13 are shaped as a disc made in
the face 5 of the resonator described earlier.
[0055] Advantageously, the resonator comprises a central hole
arranged at the centre of the face 5 and prolonged by a linking
foot 21 between the resonator 3 and the base 2. This linking foot
can have various functions and especially act as mechanical link
between the resonator and the base, and/or allow passage for
electrical connections between the modules of the base and the
piezoelectric elements. The foot is arranged inside the body the
resonator.
[0056] Advantageously, the base 2 comprises a recess of shape
complementary to the foot 21, and capable of receiving the linking
foot 21 to mechanically join the resonator and the base.
[0057] In general, the gyroscope 1 comprises an interconnection
card 20 connecting the plurality of electrical connection 15 and
being connected to the piezoelectric elements 10.
[0058] This interconnection card 20 is used for transmission of
information or commands sent by the control and processing modules
18 to the piezoelectric elements, or vice versa.
[0059] In general, part of the piezoelectric elements 10 is capable
of exciting the resonator in vibration, and the other part of the
piezoelectric elements 10 is capable of detecting vibrations of the
resonator.
[0060] Eight piezoelectric elements could be used for example,
arranged uniformly on the face 5 of the resonator 3, with four of
said elements dedicated to detecting vibrations, and four of said
elements dedicated to excitation of the resonator.
[0061] Alternatively, each piezoelectric element 10 at the same
time comprises a piezoelectric sub-element 23 capable of exciting
the resonator in vibration and a piezoelectric sub-element 24
capable of detecting vibrations of the resonator, as illustrated in
FIG. 5. In general, the sub-elements 23, 24 are arranged near or
adjacent to each piezoelectric element 10.
[0062] Advantageously, the sub-elements 23, 24 of the same
piezoelectric element 10 are arranged on the same radius of the
face 5. They are generally distinct sub-elements 23, 24 but
arranged near one another.
[0063] In general, the sub-elements 23, 24 are arranged on two
concentric circles of different radii.
[0064] These can be distinct sub-elements, arranged near one from
another, or contiguous zones of the same piezoelectric element.
[0065] In general, these are pellets, rectangular and metalized on
their two faces, one of the face being stuck or brazed on the face
of the resonator constituting the earth.
[0066] As explained earlier, the resonator is capable of vibrating
according to a first vibration mode comprising antinodes
distributed over two axes, and a second vibration mode comprising
antinodes distributed over two other axes. They are elliptical
vibration modes.
[0067] Advantageously, the face of the resonator comprises on each
axis of the first and second vibration modes two piezoelectric
elements 10, each piezoelectric element 10 at the same time
comprising at least one piezoelectric sub-element 23 capable of
exciting the resonator in vibration and at least one piezoelectric
sub-element 24 capable of detecting vibrations of the
resonator.
[0068] This finally yields at least sixteen piezoelectric elements.
This number can be limited to sixteen piezoelectric elements, with
eight elements 10 each comprising two sub-elements 23, 24.
[0069] This is a major advantage for rejecting parasite modes
occurring in the resonator, and multiplying the vibration measuring
and control points, as explained hereinbelow.
[0070] In general, the gyroscope also comprises a protective cap,
not shown, for retaining the vacuum created later under said cap
and covering the assembly comprising the resonator and the base.
The cap is for example a bell or a cylinder.
[0071] In an embodiment illustrated in FIG. 6, the face 5 comprises
a central hole 13. The resonator also comprises a linking foot 21
between the resonator 3 and the base 2, arranged at the level of
the extension of the central hole 13. The foot is arranged inside
the body of the resonator.
[0072] The foot 21 allows at least one electrical connection 15 to
pass through, thus connecting the vibration control and processing
modules 18 arranged in the base 2 and the piezoelectric elements
23, 24. The foot 21 likewise acts as mechanical linking between the
resonator 3 and the base 2, especially by way of its complementary
form with a recess 30 of the base 2.
[0073] This embodiment produces a highly compact gyroscope.
[0074] It is likewise possible to provide additional holes 13 in
the face 5, as mentioned earlier.
[0075] The invention also relates to a production process of a
vibrating gyroscope 1, such as described earlier. The process,
illustrated in FIG. 7, comprises steps consisting of: [0076]
providing a base 2 (step E1), [0077] forming a resonator 3,
comprising a body 4 of generally cylindrical form terminating in a
distal face 5, to the side opposite the base 2, said face 5
comprising at least one through hole 13 (step E2), [0078] placing a
plurality of piezoelectric elements 10 in contact with the
resonator 3, preferably on the face 5 (step E3), [0079]
mechanically assembling the resonator 3 on the base 2 (step E4),
[0080] placing, at least in part, vibration control and processing
modules 18 in the base 2 (step E5), and [0081] electrically
connecting said modules 18 of the base 2 and the plurality of
piezo-electrical elements 10, via at least one electrical
connection 15 passing through the interior of the body 4 of the
resonator 3 via said hole 13, for controlling and measuring the
vibration of the resonator 3 (step E6).
[0082] In general, the resonator 3 is fixed on the base 2 by
brazing.
[0083] In conventional terms, the process comprises a degassing
step, and a step of vacuum sealing via the protective cap covering
the assembly.
[0084] Because of the process according to the invention, the
gyroscope is much easier to make, especially at the level of the
electrical connections to be put in place, which can be made for
example by a bonding process between the piezoelectric elements 10
and the interconnection card 20.
[0085] FIG. 8 illustrates an embodiment of the vibration control
and processing in a gyroscope according to the invention.
[0086] This is especially completed by using vibration control and
processing modules 18, arranged at least in part in the base 2. Of
course, part of the modules 18 can be arranged outside the
gyroscope 1, for example on an electronic card placed near the
gyroscope 1.
[0087] In general, the vibration control and processing modules 18
are adapted to maintain the vibration of the resonator in
cooperation with the piezoelectric elements 10 and for measuring
the vibrations caused in the resonator. Most often, they comprise
one or more electric signal generators, and electric modules such
as amplifiers, filters, multipliers, adders, subtractors or the
like.
[0088] The modules 18 are adapted to process the measured signal to
deduce therefrom an angle of rotation and/or a speed of rotation
about the axis z of the cylindrical body of the resonator 3.
[0089] The modules 18 at the same time constitute a vibration
excitation circuit and a detection/treatment circuit.
[0090] In general, the excitation circuit is in closed loop to give
the excitation vibration of the resonator constant amplitude and a
pulse equal to the pulse of the fundamental vibration mode.
[0091] It is understood that various embodiments of said modules
are possible. Control and processing of vibration of the resonator
of the cylinder are widely known from the prior art. Different
types of execution are possible, for example: open-loop gyrometer
mode, closed-loop gyrometer mode, and gyroscope mode.
[0092] FIG. 8 illustrates an embodiment of control and processing
of vibration of the resonator 3 in closed-loop gyrometer mode.
[0093] The gyroscope comprises eight piezoelectric elements 10
arranged between the holes of the face 5 of the resonator 3. These
elements are advantageously shaped as rectangular pellets
distributed uniformly about the circumference of the face 5 of the
resonator 3.
[0094] An electrical signal generator 25 excites the piezoelectric
elements 10a, 10e, arranged at the level of a first axis of
antinodes of the first vibration mode of the resonator (axis
x).
[0095] A measuring unit 26 receives the signals measured by the
piezoelectric elements 10c, 10g, arranged at the level of a second
axis of antinodes of the first vibration mode of the resonator
(axis y).
[0096] The measuring unit 26 compares the amplitude of the first
vibration mode to a set value and transmits to the generator 25 a
deviation signal relative to this set point to modify the value of
the vibration excitation signals and form amplitude slave
control.
[0097] Rotation of the resonator causes a second elliptical
vibration mode 52 whereof the main axes x.sub.1, y.sub.1 are
located at 45.degree. from the axes x, y.
[0098] A measuring unit 27 receives the signals measured by the
piezoelectric elements 10b, 10f, arranged at the level of a first
axis of antinodes of the second vibration mode of the resonator
(axis x.sub.1), arranged at 45.degree. to the axes x,y.
[0099] When operating in closed loop, a processing unit 28 receives
a signal from the measuring unit 27 representing the amplitude of
the signals received by the measuring unit 27, and deduces
therefrom the excitation signals to be sent to the piezoelectric
elements 10d, 10h, arranged at the level of a second axis of
antinodes of the second vibration mode of the resonator (axis
y.sub.1) to cancel out the amplitude of the signals detected by the
measuring unit 27. The measuring unit 27 deduces a signal
representative of the angular speed of rotation .OMEGA. from the
amplitude of these excitation signals.
[0100] FIG. 9 shows another embodiment of control and processing of
the vibration of the resonator.
[0101] Each of the piezoelectric elements 10 at the same time
comprises a piezoelectric sub-element 23 capable of exciting the
resonator in vibration and a piezoelectric sub-element 24 capable
of detecting vibrations of the resonator.
[0102] The sub-elements 23, 24 are advantageously shaped as
rectangular pellets.
[0103] Alternatively, the sub-elements 23 and 24 can be made in the
form of contiguous zones of the same element 10.
[0104] The face 5 of the resonator 3 comprises on each axis of the
first and of the second vibration mode two piezoelectric assemblies
10, each piezoelectric assembly 10 at the same time comprising at
least one piezoelectric sub-element 23 capable of exciting the
resonator in vibration and at least one piezoelectric sub-element
24 capable of detecting vibrations of the resonator. The
piezoelectric elements 10 are arranged on either side of the centre
of the face of the resonator.
[0105] Here there are therefore sixteen piezoelectric elements 23,
24, eight in excitation and eight in measurements.
[0106] This embodiment rejects parasite vibration modes which might
occur in the resonator, something not possible with only eight
piezoelectric elements.
[0107] In general, for each vibration mode, the processing consists
of getting a treated signal equal to the sum of the measurements of
the piezoelectric sub-elements located on the antinodes showing
amplitude of a given sign, minus the sum of the measurements of the
piezoelectric sub-elements located on the antinodes showing
amplitude of a sign opposite the given sign, said treated signal
rejecting parasite vibration modes of the resonator. The sign of
amplitudes of the antinodes (maxima of amplitude of vibration) is
defined at one given instant of vibration, since the latter varies
alternatively.
[0108] Of course, it is possible to generalise this embodiment in
the event where the first and the second modes of vibration each
exhibit antinodes distributed over n axes, and in this case each of
the n axes comprises two piezoelectric elements 10 at the same time
comprising at least one excitation sub-element element 23 at least
one detection sub-element 24.
[0109] The four piezoelectric sub-elements 24a, 24c, 24e and 24g,
arranged according to the axes x,y of the antinodes of the first
vibration mode, supply output signals each proportional to
elongation of the vibration of the resonator and which are combined
in a subtractor 28 to supply the input signal of a slave excitation
circuit 29 of amplitude and phase.
[0110] The circuit shown by way of example comprises an amplifier
30 which attacks a multiplier 31 by way of a filter 32 piloted by a
phase regulation chain.
[0111] The gain of the multiplier 31 is controlled by the amplitude
regulation chain 33 which receives both the output signal of the
amplifier 30 and a reference signal REF, representative of the
amplitude to be maintained.
[0112] The filter 32 (active filter in general) is controlled for
its part by a phase comparator 40 which receives both the output
signal of the amplifier 30 and also the output signal of the
circuit, coming from the multiplier 31. The phase comparator 40
controls the filter 32 so as to maintain the phase difference at a
constant value, generally zero.
[0113] The output signal of the circuit 29 attacks the
piezoelectric sub-elements 23a, 23c, 23e, 23g by way of an inverter
34, inverting the polarity of signals applied to the elements 23c
and 23g.
[0114] The four piezoelectric sub-elements 24b, 24d, 24f, 24h
supply signals which are combined in a subtractor 41 to constitute
the input signal of the measuring circuit 42, in closed-loop
gyrometer mode.
[0115] The circuit 42 can have a constitution of known type.
[0116] The circuit illustrated comprises an input amplifier 43
followed by a synchronous demodulator 44 which receives a reference
signal constituted by an output signal of the circuit 29.
[0117] The demodulated signal is applied to a low-pass filter 45
whereof the output 46 is representative of the angular rotation
speed .OMEGA.. Looping in gyrometer mode is ensured by a link
between the output of the amplifier 43 and the piezoelectric
sub-elements 23b, 23d, 23f, 23h, by way of a modulator 47, an
amplifier 48 and an inverter 49 inverting the polarity of the
signals applied to the elements 23d and 23h.
[0118] The subtractors 28 and 41 and inverters 34 and 49 can be
dispensed with by appropriately orienting the polarisation vectors
of the piezoelectric pellets 23, 24 relative to each other.
[0119] As indicated earlier, the invention may have numerous
variant embodiments, especially related to the constitution of the
control and processing modules 18 linked to the mechanical
resonator.
[0120] The person skilled in the art understands that the vibration
control and processing modules 18 just now described are not
limiting for the invention, and that various implementations and
variants are possible.
[0121] As the person skilled in the art understands, the gyroscope
according to the invention is more compact, simpler and less
expensive to make. Also, it has a lower angular derive than some
gyroscopes of the prior art (around 10.degree./H in some
embodiments). Finally, the invention provides a gyroscope less
sensitive to the vibratory environment, which is a major
advantage.
* * * * *